US7791302B2 - Method for measuring a motor current - Google Patents

Method for measuring a motor current Download PDF

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Publication number
US7791302B2
US7791302B2 US12/083,756 US8375606A US7791302B2 US 7791302 B2 US7791302 B2 US 7791302B2 US 8375606 A US8375606 A US 8375606A US 7791302 B2 US7791302 B2 US 7791302B2
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Prior art keywords
current
motor
motor current
voltage
power switching
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US12/083,756
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US20090009121A1 (en
Inventor
Uwe Krause
Heinz Ludwig
Uwe Nolte
Guido Sonntag
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Siemens AG
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Siemens AG
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Assigned to SIEMENS AKTIENGESELLSCHAFT reassignment SIEMENS AKTIENGESELLSCHAFT ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: NOLTE, UWE, SONNTAG, GUIDO, KRAUSE, UWE, LUDWIG, HEINZ
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P7/00—Arrangements for regulating or controlling the speed or torque of electric DC motors
    • H02P7/06—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current
    • H02P7/18—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power
    • H02P7/24—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices
    • H02P7/28—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices
    • H02P7/285—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices controlling armature supply only
    • H02P7/29—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices controlling armature supply only using pulse modulation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/40—Testing power supplies
    • G01R31/42—AC power supplies
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2205/00—Indexing scheme relating to controlling arrangements characterised by the control loops
    • H02P2205/01—Current loop, i.e. comparison of the motor current with a current reference

Definitions

  • the invention relates to a method for measuring a current flowing through a motor, wherein a power switching section, which supplies the motor with electrical power, is controlled by means of a control unit via a pulse-width modulation signal, the pulse-width modulation signal has a switching cycle, and the motor current is determined.
  • a preferably signed measurement of the motor current for a clocked application that is to say for example an application in which the motor is operated on an H-bridge, requires a high level of circuit complexity, since both motor connections are clocked continuously, that is to say they are supplied with pulsed power, and the potential is therefore shifted with respect to evaluation electronics.
  • An H-bridge is in general an electronic circuit comprising four switches, and is preferably formed using transistors and/or power semiconductors.
  • the H-bridge converts a DC voltage to an AC voltage at a variable frequency and with a variable pulse width.
  • a circuit such as this is used in particular for driving direct-current motors and for selection of the rotation direction.
  • an H-bridge can also be used to feed a transformer from DC voltage power supply systems.
  • an H-bridge is used, for example, in modern switched-mode power supplies.
  • the clocking process results in the motor current having an alternating component whose magnitude depends on the terminal voltage, the duty ratio, or the pulse to pause ratio, of a pulse-width modulation signal and the effective inductance of the motor.
  • the measurement of any given instantaneous value of the motor current is therefore always subject to some uncertainty relating to the alternating component.
  • a plurality of measured values are recorded and are determined by means of an averaging process, for example by means of a low-pass filter with a cut-off frequency which corresponds to a fraction of the clock frequency. The measured value determined in this way is then available only with a corresponding time delay.
  • the object of the invention is to specify a method for measuring a motor current which determines the motor current at less cost and more quickly than is the case in the prior art.
  • the measured value is sampled in a supply line to the power switching section or in a supply line to the motor. There is no longer any need to take into account a potential shift between the evaluation electronics and the supply lines, which have a disadvantageous effect on the measurement result.
  • a variable which is proportional to the motor current is sampled as a representative measured value. Since the motor current can also be represented by various variables which are proportional to the motor current, it is advantageous not to measure the motor current directly, but to determine it by means of an indirect method. In comparison to a direct motor current measurement, particularly when the currents are very high, the determination of a proportional variable allows the circuit design and the metrology complexity to be kept low.
  • variable which is proportional to the motor current is formed by means of the voltage drop across a current measurement resistor.
  • introduction, for example, of a low-value measurement resistor into a supply line for the power switching section provides a simple and low-cost measurement method by measuring the voltage across a so-called shunt.
  • the voltage drop within a voltage mesh influences an input voltage of an A/D converter such that the motor current is determined by any discrepancy from a reference voltage.
  • This indirect current measurement by means of the shunt allows the current to be measured with little power being consumed.
  • a time for sampling is defined by a trigger signal from the control unit.
  • the trigger signal results in sampling synchronization by means of the A/D converter, thus making it possible to avoid the time for averaging.
  • the additional trigger signal which is determined from the pulse-width modulation signal from a pulse-width modulator allows the sampling time to be defined reliably and reproducibly.
  • the control unit allows the sampling time to be chosen freely on an application-specific basis.
  • the trigger signal In order to ensure that the sampling time corresponds as accurately as possible to the time at which the sampled value corresponds to the mean value of the motor current with a minimum discrepancy, it is advantageous for the trigger signal to be variable such that the time can be shifted in order to compensate for delay time errors.
  • a switching cycle has a pulse section with a pulse width and a pause section with a pause width, it is advantageous for the sampling time to be placed in the center of the time of one of the two cycle sections.
  • This takes account of the fact that the current ripple is always symmetrical with respect to the mean value of the current and, to a first approximation, has a linear profile.
  • the continuously rising current preferably intersects the mean value precisely in the center of a current-flow cycle. If the instantaneous value of the current is therefore recorded at the center of a current-flow cycle, then this value corresponds to the mean value of the current to be recorded, and there is additionally no need to take into account transient times in the measurement.
  • a further improvement in the measurement accuracy is achieved by placing the sampling time in the center of the time of the longer cycle section.
  • the time at the center of the respectively longer current-flow phase is preferably used for sampling purposes, in order to improve the measurement accuracy.
  • the drive direction of the power switching section is taken into account in order to determine the current direction of the motor current.
  • the motor current value determined according to the invention can accordingly be multiplied by +1 or ⁇ 1, and matches the magnitude and sign of the actual current value of the motor.
  • FIG. 1 shows a schematic illustration of a motor drive with a measurement device
  • FIG. 2 shows an overview of the time profiles of drive signals and of a voltage across a measurement resistor.
  • FIG. 1 shows a block diagram of a motor drive for a motor 1 .
  • the motor 1 is in the form of a direct-current motor.
  • the motor 1 is supplied with electrical power via the motor supply lines 9 , 9 a and via a power switching section 2 .
  • the power switching section 2 is in the form of an H-bridge.
  • a control unit 4 produces a plurality of drive signals for the power switching section 2 , via a driver 3 .
  • the control unit 4 has a pulse-width modulator 5 and an analog/digital converter 6 , the A/D converter 6 for short, which are formed by a freely configurable microcontroller.
  • the control unit 4 is supplied with the required supply voltage at a +5 V connection and a ground connection GND.
  • further functions can also be implemented in the microcontroller, for example recording of surge currents or an operating time counter.
  • the pulse-width modulator 5 is additionally designed to produce a trigger signal for the A/D converter 6 .
  • the trigger signal is passed to the A/D converter 6 via a trigger line 7 .
  • the trigger signal defines the time of sampling and measurement.
  • the A/D converter 6 In order to measure an input voltage U I — MOT , the A/D converter 6 has three inputs. The A/D converter 6 is essentially supplied with a reference voltage U ref via a first input. The input voltage U I — MOT is recorded by a further input. A third input connects the A/D converter 6 to the ground connection GND.
  • a current measurement resistor R M is arranged in the supply line 8 a to the power switching section 2 .
  • the power switching section 2 is supplied with an operating voltage U B via a further supply line 8 to the power switching section 2 .
  • a voltage divider with voltage divider resistors R 1 and R 1 ′ is arranged in parallel with the current measurement resistor R M .
  • the voltage U M which is dropped across the current measurement resistor R M may therefore be “tapped off”.
  • the voltage divider resistor R 1 is in this case connected in parallel with the inputs for the reference voltage U ref and for the input voltage U I — MOT for the A/D converter 6 .
  • the DC voltage supply for the power switching section 2 is provided via the supply lines 8 , 8 a to the power switching section 2 .
  • the supply line 8 supplies the power switching section 2 with the positive operating voltage U B .
  • the power switching section 2 is connected to the reference-ground potential GND via the supply line 8 a to the power switching section 2 .
  • the motor 1 to be driven is located, in terms of circuitry, in a center branch between a left-hand and a right-hand bridge arm of the H-bridge.
  • a first switch S 1 is arranged in the left-hand bridge arm, and a second switch S 2 is arranged connected in series.
  • a third switch S 3 is arranged in the right-hand bridge arm, and a fourth switch S 4 is likewise arranged in series.
  • the two bridge arms form a parallel circuit.
  • the four switches S 1 to S 4 are preferably metal-oxide semiconductor field-effect transistors. Field-effect transistors such as these have control inputs. The relevant field-effect transistors can be switched on and off via these control inputs by means of the appropriate drive signals from the control unit 4 .
  • the respectively diagonally opposite switches for example S 2 and S 3 , are closed by the control unit 4 . While the switches S 2 and S 3 are closed, the switches S 1 and S 4 remain open since, otherwise, this would result in the supply voltage U B being directly shorted.
  • the current I MOT in this switch position, flows via the supply line 8 to the power switching section 2 via the switch S 3 , via the supply line 9 a to the motor 1 , through the motor 1 , via the supply line 9 from the motor 1 , via the switch S 2 , via the current measurement resistor R M to ground GND. This results in a specific rotation direction, as well as a torque from the motor 1 .
  • the current I MOT flows through the motor 1 in the opposite direction.
  • the motor is therefore driven in the opposite direction.
  • the power of the motor 1 can be regulated and its rotation speed can be controlled by variation of the pulse width of the pulse-width modulation signal.
  • the voltage divider resistors R 1 and R 1 ′ each have values of 10 k ⁇ .
  • the current measurement resistor R M has a resistance of 1 ⁇ .
  • the voltage U R1 ′ corresponds to the input voltage U I — MOT to the A/D converter 6 .
  • a current I MOT flows via the H-bridge and via the motor 1 .
  • the rising motor current I MOT causes a voltage drop U M across the current measurement resistor R M .
  • This voltage drop U M across the current measurement resistor R M changes the voltage drop across the voltage divider resistor R 1 .
  • the voltage drop U I — MOT at the measurement input of the A/D converter 6 also changes. If the current to the motor 1 increases, the voltage U I — MOT at the A/D converter 6 rises proportionally. If the current to the motor 1 falls, the voltage U I — MOT at the A/D converter 6 falls in a corresponding manner.
  • the value determined in this way can be converted by multiplication by +1 or ⁇ 1, depending on the respective drive direction via the H-bridge and the sampling of the analog value in the center of a current-flow cycle, directly to the signed mean value of the motor current I MOT .
  • the discrepancy between U I — MOT and U ref /2 is proportional to the voltage U M across the current measurement resistor R M , and the current value.
  • I MOT is correspondingly proportional to the voltage U M , and can therefore be determined.
  • FIG. 2 shows the characteristic profiles of the drive signals that have been produced by means of the pulse-width modulator 5 shown in FIG. 1 .
  • a pulse-width modulation signal 10 or PWM signal 10 for short, for driving the H-bridge has a switching cycle 15 with a pulse width 16 and a pause width 17 .
  • a trigger signal 11 is derived from the PWM signal 10 from the pulse-width modulator 5 in order to define a sampling time A 1 , A 2 .
  • the trigger signal 11 has a falling flank at the point A 1 which triggers the A/D converter 6 to sample the input voltage U I — MOT . This trigger signal 11 is passed via the trigger line 7 to the A/D converter 6 in FIG. 1 .
  • the figure shows a drive signal 12 for the switches S 2 and S 3 , and a further drive signal 13 for the switches S 1 and S 4 .
  • the drive signals 12 and 13 each overlap in time at the start and end of the pulse width 16 and of the pause width 17 with an application-specific dead time. This dead time is used to avoid the switches S 1 to S 4 being closed at the same time.
  • the dead time is “positive” while a “negative” dead time is used for a current intermediate circuit, that is to say a deliberate overlap is produced, during which both signals are at a positive drive potential.
  • the motor current value I MOT or the input voltage U I — MOT to the A/D converter 6 is sampled in the center A 1 of the time of the pause width 17 .
  • the continuous rise of the motor current I MOT and the voltage profile 14 during a pause width 17 corresponds to a linear rise, which is symmetrical with respect to the center of the time of the pause width 17 .
  • the instantaneous value determined in this way corresponds, to a good approximation, to the mean value of the motor current I MOT .

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Direct Current Motors (AREA)
  • Measurement Of Current Or Voltage (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
  • Control Of Electric Motors In General (AREA)
US12/083,756 2005-10-18 2006-10-17 Method for measuring a motor current Active 2027-09-11 US7791302B2 (en)

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
DE102005050130 2005-10-18
DE102005050130 2005-10-18
DE102005050130.3 2005-10-18
DE102006047707 2006-10-09
DE102006047707A DE102006047707A1 (de) 2005-10-18 2006-10-09 Verfahren zur Messung eines Motorstromes
DE102006047707.3 2006-10-09
PCT/EP2006/067484 WO2007045645A2 (de) 2005-10-18 2006-10-17 Verfahren zur messung eines motorstromes

Publications (2)

Publication Number Publication Date
US20090009121A1 US20090009121A1 (en) 2009-01-08
US7791302B2 true US7791302B2 (en) 2010-09-07

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Application Number Title Priority Date Filing Date
US12/083,756 Active 2027-09-11 US7791302B2 (en) 2005-10-18 2006-10-17 Method for measuring a motor current

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US (1) US7791302B2 (es)
EP (1) EP1949114B1 (es)
AT (1) ATE432476T1 (es)
DE (2) DE102006047707A1 (es)
ES (1) ES2325793T3 (es)
WO (1) WO2007045645A2 (es)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090302794A1 (en) * 2008-05-16 2009-12-10 Chen-Ku Wei Torque control circuit for electrical motor
US9281770B2 (en) 2012-01-27 2016-03-08 Ingersoll-Rand Company Precision-fastening handheld cordless power tools

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103703793B (zh) * 2012-06-26 2015-02-18 本多电子株式会社 机电转换元件及其制造方法
DE102015200654B4 (de) * 2015-01-16 2018-12-27 Deutsches Zentrum für Luft- und Raumfahrt e.V. Verfahren zur Kompensation parasitärer Induktivitäten in Strommesswiderständen
JP6361562B2 (ja) * 2015-04-17 2018-07-25 株式会社デンソー モータ制御装置、及び、電動パワーステアリング装置
JP6641794B2 (ja) * 2015-08-28 2020-02-05 株式会社リコー モータ駆動装置、モータ制御装置、搬送装置及びモータ駆動方法
CN115372680A (zh) * 2022-08-22 2022-11-22 深圳市麦格米特驱动技术有限公司 一种充电电流采样方法

Citations (8)

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Publication number Priority date Publication date Assignee Title
US4866356A (en) * 1987-06-25 1989-09-12 Siemens Aktiengesellschaft Circuit for controlling the speed of a subfractional horsepower DC motor
US5689162A (en) * 1995-06-07 1997-11-18 Sgs-Thomson Microelectronics, Inc. Apparatus and method for current sensing for motor driver in pwm mode
US5930103A (en) 1998-03-02 1999-07-27 Motorola, Inc. Control circuit for an electromechanical device
US6424799B1 (en) * 1993-07-06 2002-07-23 Black & Decker Inc. Electrical power tool having a motor control circuit for providing control over the torque output of the power tool
US20020121871A1 (en) * 2001-03-02 2002-09-05 Matsushita Electric Industrial Co., Ltd. Disk drive apparatus and motor
US20060119300A1 (en) * 2004-10-29 2006-06-08 Zetex Semiconductors Plc Method of controlling a brushless DC motor
US20060125431A1 (en) * 2004-12-11 2006-06-15 Ebm-Papst St. Georgen Gmbh & Co. Kg Method and arrangement for controlling the synchronous running of a plurality of electronically commutated motors
US20090251084A1 (en) * 2008-04-05 2009-10-08 Benjamin Haas Electronically commutated motor

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4866356A (en) * 1987-06-25 1989-09-12 Siemens Aktiengesellschaft Circuit for controlling the speed of a subfractional horsepower DC motor
US6836614B2 (en) * 1993-07-06 2004-12-28 Black & Decker Inc. Electrical power tool having a motor control circuit for providing control over the torque output of the power tool
US6424799B1 (en) * 1993-07-06 2002-07-23 Black & Decker Inc. Electrical power tool having a motor control circuit for providing control over the torque output of the power tool
US7112934B2 (en) * 1993-07-06 2006-09-26 Black & Decker Inc. Electrical power tool having a motor control circuit for providing control over the torque output of the power tool
US20020153856A1 (en) * 1993-07-06 2002-10-24 Gilmore Alan A. Electrical power tool having a motor control circuit for providing control over the torque output of the power tool
US20040217727A1 (en) * 1993-07-06 2004-11-04 Gilmore Alan A Electrical power tool having a motor control circuit for providing control over the torque output of the power tool
US5689162A (en) * 1995-06-07 1997-11-18 Sgs-Thomson Microelectronics, Inc. Apparatus and method for current sensing for motor driver in pwm mode
US5930103A (en) 1998-03-02 1999-07-27 Motorola, Inc. Control circuit for an electromechanical device
US6680593B2 (en) * 2001-03-02 2004-01-20 Matsushita Electric Industrial Co., Ltd. Disk drive apparatus and motor
US20020121871A1 (en) * 2001-03-02 2002-09-05 Matsushita Electric Industrial Co., Ltd. Disk drive apparatus and motor
US20060119300A1 (en) * 2004-10-29 2006-06-08 Zetex Semiconductors Plc Method of controlling a brushless DC motor
US20060125431A1 (en) * 2004-12-11 2006-06-15 Ebm-Papst St. Georgen Gmbh & Co. Kg Method and arrangement for controlling the synchronous running of a plurality of electronically commutated motors
US7268502B2 (en) * 2004-12-11 2007-09-11 Ebm-Papst St. Georgen Gmbh & Co. Kg Method and arrangement for controlling the synchronous running of a plurality of electronically commutated motors
US20090251084A1 (en) * 2008-04-05 2009-10-08 Benjamin Haas Electronically commutated motor

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090302794A1 (en) * 2008-05-16 2009-12-10 Chen-Ku Wei Torque control circuit for electrical motor
US7936140B2 (en) * 2008-05-16 2011-05-03 Mobiletron Electronics Co., Ltd. Torque control circuit for electrical motor
US9281770B2 (en) 2012-01-27 2016-03-08 Ingersoll-Rand Company Precision-fastening handheld cordless power tools

Also Published As

Publication number Publication date
US20090009121A1 (en) 2009-01-08
DE502006003846D1 (de) 2009-07-09
WO2007045645A2 (de) 2007-04-26
WO2007045645A3 (de) 2007-06-28
EP1949114B1 (de) 2009-05-27
ES2325793T3 (es) 2009-09-17
DE102006047707A1 (de) 2007-04-26
EP1949114A2 (de) 2008-07-30
ATE432476T1 (de) 2009-06-15

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